The present invention relates to a saber saw, and more particularly, to a saber saw that inclines the front end of a blade to a workpiece when the blade withdraws toward a housing so as to make sawtooth further cut into the workpiece to increase sawing efficiency.
Saber saws are reciprocating type cut-off tools driven by an electric-powered motor, which are used to cut off woody and steel workpieces, pipes, etc. in constructing residences and buildings, or furnishing, remodeling, and scrapping works. As is generally known, a saber saw cuts off a workpiece to be sawed by reciprocating a reciprocation shaft (hereinafter simply referred to as a plunger) which has a straight sawtooth (hereinafter simply referred to as a blade) attached to the leading end of the plunger.
In view of motion of the plunger in sawing operation, saber saws are classified into the first and second types. According to the first type, a plunger simply reciprocates along its axis direction. According to the second type, a plunger reciprocates as well as wobbles upward and downward so that sawtooth of the blade can further cut into a workpiece to facilitate sawing operation. The sawing operation in which the blade moves under the motion combining the reciprocating motion and the wobbling motion in cutting off a workpiece is referred to as orbital sawing operation.
FIG. 16 shows a partly cross-sectional view of a conventional saber saw 401 for use in performing the orbital sawing operation. When a drive gear 412 that is concentrically arranged on a rotor of a motor rotates, a secondary shaft 413 rotates with reduced speed through a driven gear 414. The secondary shaft 413 is integrally provided with an eccentric cylinder shaft 413A, and a recipro-plate or reciprocating-plate 418 is attached to the secondary shaft 413 for converting rotational motion to reciprocating motion. A saber saw body 402 has attached thereto an elongated guide sleeve 421 of irregular-shaped cross-section. The guide sleeve 421 is pivotally movable about a supporting pin 422. Inside the guide sleeve 421, A plunger 420 is slidably movable relative to an inner peripheral surface of the guide sleeve 421. The plunger 420 has a leading end provided with a blade 19. The plunger 420 is connected to a spherical portion 418B of the swinging recipro-plate 418. Upon rotation of the secondary shaft 413, the recipro-plate 418 swings backward and forward, which permits the plunger 420 to reciprocate along its longitudinal axis. At the rear end of the guide sleeve 421, a linking plate 423 extends downward. A free end of the linking plate 423 is positioned in contact with the eccentric cylinder shaft 413A.
In sawing operation, sawing reaction force F1 applied to the blade 19 causes the rear end of the guide sleeve 421 to pivotally move downward about the supporting pin 422, and thus the lower end of the linking plate 423 is pressed against the eccentric cylinder shaft 413A. So, when the eccentric cylinder shaft 413A rotates in consequence of rotation of the secondary shaft 413, the rear end of the guide sleeve 421 is pushed upward by the linking plate 423. As a result, the plunger 420 reciprocates as well as wobbles upward and downward through the guide sleeve 421.
An elliptical orbit as shown in FIG. 17 is provided as a moving locus of the tip end of the blade 19 that moves under the motion combining the reciprocating motion and the wobbling motion when the phase angle of the eccentric cylinder shaft 413A against the plunger 420 is desirably set up. The sawing operation in which the blade 19 forms an elliptical orbit is referred to as the orbital sawing operation. In the orbital sawing operation, when the blade 19 is withdrawn toward the saber saw body 402, the blade 19 moves into a workpiece W, which significantly increases sawing efficiency especially in sawing a comparatively tender workpiece such as a woody material. Above-described conventional saber saws are disclosed in laid open Japanese Patent Application Publication Nos. S51-130983, 2000-263504, and 2002-79417.
In the conventional saber saw 401, so as to make the plunger 420 reciprocate along its axial direction as well as wobble upward and downward, the prolonged and irregular-shaped guide sleeve 421 is required. Being long and of irregular shape, the guide sleeve 421 becomes heavy and requires troublesome works in production, which undesirably makes the whole saber saw 401 heavy and requires high production cost. Furthermore, so as to make the guide sleeve 421 wobble, a gap is provided between the saber saw body 402 and the guide sleeve 421. However, cutting chips and water may be entered into the saber saw body 402 through the gap. The cutting chips are brought about when sawing a workpiece, and water droplets are brought about when sawing an existing water pipe containing water. This undesirably leads to abrasion and corrosion of internal parts and therefore shortens the service life of the saber saw 401. In order to avoid this problem, a cylinder-shaped seal member 421A made of a special rubber material is interposed in the gap as shown in FIG. 16. However, because the seal member 421A is made from a special material production cost is increased. Further, assembly cost is also increased. Furthermore, since the seal member 421A is repeatedly deformed when the guide sleeve 421 wobbles, there is raised problem from the viewpoint of durability.